Step-by-step Guide to Growing Tomatoes from Seed in Ireland

(With Expert Tips for Bush & Cordon Types)

Growing tomatoes in Ireland requires a little strategy — but with the right timing, warmth, feeding and pruning, you can harvest beautifully sweet tomatoes from July right into autumn.

Because of our cool springs, damp summers and risk of blight, success depends on:

• Choosing the right varieties

• Starting seeds at the right time

• Managing watering carefully

• Understanding whether your plant is determinate (bush) or indeterminate (cordon)

This guide walks you through every stage — from seed to harvest.

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Step 1: Choose the Right Variety for Ireland

Ireland’s shorter, cooler growing season means variety choice matters.

🌿 Outdoor & Early or Easy-to-Grow Varieties

• Boulette de Touraine – Classic French type; garden hardy and good for salads and slicing.

• Hundreds and Thousands Cherry Tomato – Small cherry fruits; productive, colourful, and excellent fresh.

• Olivine Orange Cherry Tomato – Bright orange cherry; sweet flavour.

• Brad’s Atomic Grape Tomato – Cherry/grape type with vibrant colour and bite.

• Blue Berries Tomato – Unique blue-violet fruits; excellent flavour and visual interest.

• Mila Tomato – Heirloom garden tomato; versatile.

• Royal Finger Tomato – Unusual elongated fruit.

• Santorini Paste Tomato – Paste type good for sauces and preserving.

🌱 Dwarf or Small Garden Varieties

• • Tomato Dwarf Stony Brook Heart – Dwarf heart-shaped fruit, good for containers.

  • Tomato Dwarf Sneaky Sauce – Dwarf sauce type, perfect for small spaces.

  • Dwarf TastyWine Tomato – Dwarf wine-style flavourful tomato.

  • Micro Dwarf Tomato Birdie Rouge – Very small plant for indoor pots or patios.

  • Mini Dwarf Tomato Floragold Basket – Basket-friendly dwarf cherry.

  • White Wonder Tomato – Light-coloured heirloom; sweet and distinctive

Tip: If growing outdoors without protection, choose early-maturing varieties (55–65 days to maturity).

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Step 2: When to Sow Tomato Seeds in Ireland

Timing is crucial.

• Mid–late March – Sow for greenhouse growing.

• Late March–early April – Sow for outdoor crops.

Tomatoes need about 6–8 weeks indoors before planting out.

Do not sow too early — weak light in February causes leggy plants.

Ideal germination temperature: 18–22°C.

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Step 3: How to Sow Tomato Seeds

You will need:

• Seed trays or small pots

• Fine seed compost

• Warm bright location

Method

1. Fill containers with moist compost.

2. Sow seeds 0.5cm deep.

3. Cover lightly.

4. Water gently.

5. Place somewhere warm.

Seeds usually germinate within 5–10 days.

Tip: Adding a thin layer of vermiculite helps maintain moisture and prevents surface crusting.

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Step 4: Light Is Critical

As soon as seedlings emerge:

• Move them to the brightest possible location.

• A south-facing windowsill is ideal.

• Rotate trays daily to prevent leaning.

Leggy seedlings = insufficient light.

If needed, use grow lights for 12–16 hours daily.

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Step 5: Potting On & Deep Planting

When seedlings develop their first true leaves:

1. Lift gently.

2. Pot into 9cm pots.

3. Bury stems deeper than before.

Tomatoes produce roots along buried stems — deeper planting makes stronger plants.

Continue potting on as roots fill containers.

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Step 6: Understanding Determinate vs Indeterminate Tomatoes

This is one of the most important decisions for Irish growers.

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Determinate Tomatoes (Bush Types)

Determinate plants grow to a fixed height and produce fruit over a shorter, concentrated period.

Characteristics

• Compact and bushy

• 60–120cm tall

• Fruit ripens mostly at once

• Little to no pruning required

Irish Growing Advantages

✔ Often earlier cropping
✔ Good for outdoor growing
✔ Suitable for containers and grow bags
✔ Useful for sauce-making and preserving

Care Tips for Determinate Types

• Do NOT remove side shoots.

• Provide light staking or cages.

• Feed consistently once flowering begins.

• Remove only yellow or diseased leaves.

Because they finish earlier, bush varieties can sometimes avoid late-season blight pressure outdoors.

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Indeterminate Tomatoes (Cordon / Vine Types)

Indeterminate tomatoes continue growing and producing until frost stops them.

These are the most common greenhouse types in Ireland.

Characteristics

• Tall (1.8–2.5m+)

• Continuous harvest

• Require training and pruning

• Need strong support

Irish Growing Advantages

✔ Longer harvest season
✔ Higher yield per plant
✔ Ideal for greenhouses and polytunnels

Care Tips for Indeterminate Types

• Remove side shoots weekly.

• Train to a single stem.

• Tie to canes or string supports.

• Pinch out the growing tip in late August (after 4–6 trusses outdoors, 6–8 in greenhouse).

• Remove lower leaves as fruit ripens to improve airflow.

Ventilation is essential in Irish conditions to reduce humidity and fungal risk.

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Step 7: Hardening Off

Before planting outdoors:

• Place plants outside during the day.

• Bring them in at night.

• Do this for 7–10 days.

Never rush this step — Irish late frosts are common.

Plant outdoors only after frost risk has passed (usually late May).

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Step 8: Planting Out

Greenhouse / Polytunnel

Plant late April to May.

Outdoors

Plant late May to early June.

Spacing:

• 45–60cm apart.

Add:

• Well-rotted compost or manure.

• Strong supports at planting time.

Plant deeply and water thoroughly.

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Step 9: Feeding Properly

Tomatoes are heavy feeders.

• Start feeding once first flowers appear.

• Use a high-potash tomato fertiliser weekly.

• Avoid high nitrogen feeds (too leafy, fewer fruits).

Container plants require more consistent feeding than in-ground plants.

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Step 10: Watering Correctly

Inconsistent watering causes:

• Blossom end rot

• Fruit splitting

• Poor fruit set

Best practice:

• Water deeply at the base.

• Keep soil evenly moist.

• Avoid wetting foliage.

• Mulch to regulate moisture.

In hot greenhouse weather, daily watering may be necessary.

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Step 11: Preventing Common Irish Problems

Blight

More common in wet summers.

• Remove infected leaves immediately.

• Ensure good airflow.

• Avoid overcrowding.

• Do not grow near potatoes if possible.

Blossom End Rot

Caused by irregular watering.

• Maintain steady moisture.

• Avoid letting pots dry out fully.

Poor Pollination

In greenhouses:

• Gently tap flowering trusses.

• Open vents daily.

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Step 12: Harvesting & Season Extension

• Cherry tomatoes ripen first (July).

• Larger fruits follow (August–September).

• Pick regularly to encourage more fruit.

To extend the season:

• Use fleece during cold nights.

• Pinch out tops in late summer.

• Ripen green tomatoes indoors if necessary.

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Quick Comparison: Bush vs Cordon

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Final Irish Growing Strategy

For best results in Ireland:

• Grow determinate outdoors for early security.

• Grow indeterminate in a greenhouse for extended harvest.

• Prioritise airflow and consistent watering.

• Choose early-maturing varieties.

• Do not sow too early.

With warmth, light, and steady care, tomatoes can be one of the most productive crops in an Irish garden.